Method of hydraulically expanding hollow rivets



Feb 27, 319511 e. D. RODGERS METHOD OF \HYDRAULICALLY EXPANDING HOLLOW RIVETS Filed April 16,- 1941 FI' All INVENTOR gens. I flw ATTORNEYS Patented Feb. 257, 1951 METHOD OF HYDRAULICALLY EXPANDING HOLLOW RIVETS George D. Rogers, United States Army, Washington, D. C.

Application April 16, 1941, Serial No. 388,769

(Granted under the act of March 3, 1883, as amended April 30, 1928; 370 0. G. 757) 4 Claims.

The invention described herein may be manufactured and used by or for the Government for governmental purposes, without the payment to me of any royalty thereon. This invention "relates'to' an explosive unit which is particularly adapted for use as a rivet of the type shown in U. S. Patents 1,400,401 and 2,080,220.

In employing explosive rivets of the open end type it has been noted that the powder gases from the expanding charge deleteriously affect the metal of the plates that are united, and, in confined spaces, interfere with the comfort of the operator. It has also been noted that failure of a joint or connection may be attributed to improper or non-uniform deformation of the expanded end of the rivet.

The purpose of this invention is to provide a novel method of forming the rivet to insure uniform centering of the chamber within the rivet shank for containing the expanding material and uniform strength and thickness of the side walls of the chamber.

Another purpose is to provide a structure which will permit the utilization of either fluid or solid expanding mediums.

The specific nature of the invention as well as other objects and advantages thereof will clearly appear from a description of a preferred embodiment as shown in the accompanying drawings in which:

Fig. l is a longitudinal sectional view of the rivet before being expanded.

Fig. 2 is a similar view after expansion.

Figs. 3'to 6 are longitudinal sectional views illustrating steps in the fabrication of the rivet.

Figs. '7 to 9 are similar views showing steps of another method of forming the rivet.

Figs. 10 and 11 are similar views showing steps of another method.

Fig. 12 is an enlarged longitudinal sectional view of portions of the rivet and a cooperating fluid injector unit illustrating a method of application.

Referring to Figs. 1 and 2 the rivet comprises a head and a shank 6 which is adapted to be inserted in the customary manner through apertures I and 8 formed respectively in plates 9 and Ill. The head 5 is formed or provided axially with a constricted passage I i which is in communication with a chamber l2 in the shank. The chamber I2 is preferably gradually enlarged toward the end of the shank remote from the head 5. The passage ll may be enlarged somewhat at its outer extremity. The interior of the rivet may be filled, as shown in Figure 1, for example, with any material which may be used in the application of pressure to expand the rivet 2 to a condition such as shown in Figure 2, whereby the plates 9 and 10 will be secured to each other. In the embodiment of the invention shown in Fig. 1 chamber I2 is filled with an explosive material I, such as nitrocellulose, and the passage II is filled with any suitable priming material 2, for example, black powder, which can be retained in place by the application of any suitable binder to the exposed portion of the priming material 3.

The rivet is applied by placing it in position through the plates to be secured and exploded by the application of heat Or friction to the exposed priming material. The resulting explosion of the material I under partial confinement thus causes the expansion of the shank of the rivet to the shape shown in Figure 2 whereby the plates 9 and It! will be firmly secured to each other.

In an alternative manner of employment of the invention, means are provided whereby any fluid material may be fed hydraulically into the rivet under pressure to cause it to swell and anchor itself into place. In this manner of employment the passage communicating with the interior of the rivet is shaped to cooperate with a hydraulic nozzle H! which is introduced into the passage as shown in Fig. 12. Obturation is secured by the expansion of the thin elastic wall at the tip of the nozzle. Other well-known methods of effecting a seal may be applied. The chamber will preferably be filled with a pressure transmitting medium in the course of manufacture.

In a further form of the invention it is contemplated that the cavity in the rivet will be fil ed with a material which on the establishment of a predetermined condition will swell and thus expand the rivet. As an example a material which expands on freezing could be thus employed and frozen in place by the application of Dry Ice or the like.

It is also contemplated that the rivet may be filled with a solid or pulverous material in dry condition which may combine with a fluid plasticizing medium injected during expansion of the rivet to form a plastic compound which will remain in the rivet. The pressure necessary to expand the rivet could be supplied by the injection of the plasticizing medium in a manner similar to that described above in the discussion of the expansion of the rivet by injection of a hydraulic pressure transmitting medium. It is also contemplated that the dry pulverous material be of such character that it will swell when saturated with the fiuid plasticizing medium and this swelling as the fluid medium saturates the billverous material will furnish the expanding force for the rivet.

It is essential to the proper expansion of the rivet that it be so formed as to insure a uniform centering of the chamber and that the wall thickness be carefully controlled. This end may be achieved in practice by several methods. Die forming is a desirable method in that it compacts the material to uniform density and insures that the side walls will be of uniform strength as well as of uniform dimensions. In a preferred embodiment, the material of which the rivet is to be formed is received in the form of cupshaped blanks which are, in the first operation, drawn into the shape shown in Fig. 3. In the next operation the cup is upset and the material forced into a die of such form that the exterior of the cup is tapered to the form shown in Fig. 4 and the wall thickened at the open end. The head may be formed in a forming die to a shape such as shown in Fig. 5. In a subsequent press operation a sizing die shapes the shank to finished diameter with incident tapering of the walls of the chamber l2 and a head forming die having a stud set therein reforms the head and shapes the passage H.

Depending upon the material with which the cavity is to be charged the loading operation can be carried out at the close of the operations indicated in either Figures 5 or 6. In the former case the material is charged into the cavity shown in Figure 5, in either fluid or solid state. The final press operation consolidates the filling material with the result that the rivet thus formed is filled with a homogeneous material, free from air bubbles which might cause erratic expansion. In case the cavity is to be charged with finely granulated smokeless powder the loading operation may be carried out after the forming operations are completed. The loading operations can either be carried out on straight line workboard or by dial press. In either case the operations are substantially as follows: first, measure the explosive charge and charge it into the cavity; second, consolidate the charge in any desired way; third, measure the priming charge and charge into the passage I I and fourth, after suitable consolidation of the primer, seal with the binding agent unless the primer was charged wet in which case it may be self-retaining. The size of the charge to be used is dependent on the size of the rivet and the strength of the material used.

Another method insuring uniform centering of the chamber in the rivet accomplishes the desired result by piercing the blank l3 shown in Figure 7 to produce a flange indicated at l5 in Fig. 8 coaxial with the shank of the rivet l4, and of uniform thickness. Subsequent operations with a sizing die partially close the flange about the axis of the shank to form a cavity as indicated at I! in Figure 9 and a head 19 is formed in any known manner.

A somewhat similar method to that described above is illustrated in Figures and 11. In the practice of this method a blank I3, Fig. 7, is upset to form a flange 16, Fig. 10, coaxial with the shank l4 and of substantially uniform thickness. This flange may be closed to form the cavity l'l substantially as described above.

I. claim:

1. The method of riveting which consists in inserting through the parts to be secured a rivet having a chambered shank and a constricted passage in communication tharewith, applying the nozzle of a hydraulic injector unit to said passage in sealing relationship and injecting fluid through said nozzle and said passage under suf- 4 ficient pressure to stress the material of the chambered shank beyond the elastic limit thereof without exceeding the yield point.

2. The method of expanding a rivet having a chambered shank at least partially filled with a fluent material which consists in the steps of engaging with the rivet in sealed relationship a hydraulic injector nozzle communicating with the chamber, and injecting through said nozzle a iiuent material under suificient pressure to stress the material of the chambered shank beyond its yield point.

3. The method of expanding a rivet having a chambered shank with a constricted passage in communication therewith which consists in the steps of inserting into the passage in engagement with the walls thereof a thin walled obturating nozzle, and injecting a fluent material through the nozzle into the chamber under sufiicient pressure to stress the material of the chambered shank beyond its yield point.

4. The method of riveting which consists in the preliminary step of substantially filling a rivet having a chambered shank and a con-- stricted passage in communication therewith with a fluent material, inserting the rivet through the parts to be secured followed by the steps of applying the nozzle of a hydraulic injector unit to said passage in sealing relationship, applying pressure to maintain said nozzle in said sealing relationship and while said sealing relationship is so maintained, injecting fiuent material through said nozzle and said passage under sufficient pressure to stress the material of the chambered shank beyond the elastic limit thereof without exceeding the yield point.

GEORGE D. ROGERS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS W Number Name Date 887,175 Abbott May 12, 1908 960,244 Allen June 7, 1910 1,329.144 Rypinski Jan. 27, 1920 1,382,906 Gravel] June 28, 1921 V) 1,400,401 Allan Dec. 13, 1921 1,456,403 Ranney May 22, 1923 1,646.431 Tomkinson Oct. 25, 1927 1,830,722 Smith Nov. 3, 1931 1,840,928 Anthony Jan. 12, 1932 1,864,377 Sieffert June 21, 1932 1,945,480 Deems Jan. 30, 1934 2,030,165 Huck Feb. 11, 1936 2,080,220 Butter et al May 11, 1937 2,162,164 Febrey June 13, 1939 m 2,170.556 Frost Aug. 22, 1939 2,183,543 Cherry Dec. 19, 1939 2,213,818 Krause Sept. 3, 1940 2,223,964 Naoum Dec. 3, 1940 FOREIGN PATENTS Number Country Date 4,453 Great Britain Feb. 22, 1898 467,515 Great Britain June 17, 1937 689,584 Germany Mar. 28, 1940 OTHER REFERENCES Engineering Record, vol. 63, Feb. 4, 1911, advertisement of MacArthur Concrete Pile ant; Foundation Co. (Available in Div. 33 or through photostatic copy.) 

